Electrostatic lens for cathode-ray tubes



May 12, 1953 .A. D. GlAccHET-n ELEcTRosTATIc LENS Foa cATHoDERAY TUBES Filled Jan. 19. 1952 May 12, 1953 A. D. GxAccHETTl A2,338,559

ELEUTROSTATIC LENS FOR cATHoDE-RAY TUBES l Filed Jan. 19, 1952 '2 Sheets-Sheet 2 Patented May 12,1953

iLTENT f poration ofiinois Attenuation laniiary 19, 1952, vSeialNo."167,291

( oi. eisest i The present invention relates yto iel'etron fl'efn's systems for 'cathode ray picture vtubes, and ce'rns itself more particularl'ylivithimprovements in electrostatic focusing apparatus which runor`tions in a dual purpose capacity jas .a getter mount. l

In the construction of conventionally designed electron giinessemblies ift-nas become'eustoiiieijy tO--provide a isuccessive'serieseof paraxialni'e llic Cylinders or thimbles which perff'im'pliimaryanbl intermediate v'ano tieliaceeleration :erfeotsiluoonitne scanning beam. Lens discs cai-fried fb'y -on 'of vthese thiinbles-induee ai focusing faction up f beam beiore'tlfl'e la'tt'erpasses into Ythe gio'n "f Seann'ingdeflection In connection Withlel' W gun systems, the use of multi-potential le ments lin 'diie'ie'rit sequences of 'ara-'g have-beenundrstoodtoexert-conv 'g t-'ef cts upon the scannin'gbeam, 'whereby'toa cardinal `purposeofIcotieentrating enovuimir-iisiif vin/g thefcrossJsectionalbeam Sarea'tofa virtual -point t crossesectin Iat i its "destination, 3the screen surface.

When the lgun system includ-ese uevicelifo'rt-prm ducing deflection of the l'generated 'beam as ior example, to serve theifpurpose of iontrappin'g, the faxial realignment'of the be'am islfre'quently achieved by 'electronriagneticfrather thannby electtrostatic regulation. v"Following theintrapping apparatus inra sequencey of le'nst-anode elements, it is most often requisite that the -be'am belsibe jecte'd to a multiple .lens system forth'e reestablishment Aof parax-ial "and convergent aution lin order to .achieve the .proper wphysicalfdirnensions andintensity of the'beam. `In such systernsfthere havel heretofore beenutilized va .pair of equi-po= tential lens :elements between which Wasldisp'osed a thick lens whichlgaveto'the assembly afper=` formance resembling a direct and -invertedfilens system in sequence.

Underfother systems-'of focusing beam realignment, an external magnetic coil has been v4used for accomplishing this purpose, but--becaus'eof -thedistancethrough which its fiield was required `to exertan influence, thesize and-'coppercontent yoffs'uch acoil constituted ane-element of isubstan= ltial c'ostconsideration.

-Ith'azs rbe'ein ifouridfthatby locating 'a'vrelatively wide aperture lens' Yright vbetween the lensrings fof a 'uni-po'i'ientiallensisystem,1a"convergent 'in-'- fluence of remarkable effectiveness ris aecomfpli'shed with lth'e potential f of the Wadded''elef'ztrode 'ring preferably higher but' having creditable-per-` formance u'ndera Variety of co'ntr'astingpotentialsmcluuingizerio. ALBy-zlocatir'igf.tnisvringfui this ofgettercartidges. YY1Iii this respect the lens ring serves afi'iiial-ffunctin. 'By reason of `the fact'tha't be accomplished Without -tlieV 'otherwise neces- Ae ruiiigly-a principal 'objeetof 'the present invention ifs-to achieveen improved 'type of piciturfe tube @gun a's'semblf `in wliieh a highly om; cient soliver-'gente lens rings of t 'ns Y-is 'mounted between 'the nt nel terminal lens sys'- whiohlfornis 'saidlen-'s eiveiidation pellets or 4g' tersjW- hich-a more instantaneously fr'e'spo'r'rn sive' to induction heating.

Another object of the present invention is vto a@oormilislfi :an improved picture tube -lg'fun 'asvsembly'in -W-hieh'asingle annular element supported'onpostextensions which surround an ion trap i struetureiszmade'- toser've the fdualipurpose of ni'ountingla :series f-'ofJgett'erpellets to -be fired rduringtlielfo'rmativefassenibling of the tube thereafter r`to "e'X'ert f'a :scanning beami'regula'tion electrostati'cally as a lens' factor.

Oth'er objects and purposes oit-the.pres'entii'iventon are such as will become apparent during the courseof vthe following detailed -desriptiom and :suoli as will be revealed -from a y reading ci the hereunto appended claimsa .Fora bettrunderstanding, reference will now be `had 'to the aceompan'ying drawings wherein similarireference numerals designate corresponde ing .parts throughout gandwherein Fig-.f1 afside yelevational 'vi-ew of' alportion of 'a .televisionflcathode ray tube with :parts broken away tof 'reveal' the elementsV of the gun structure, includinglthep-'r'esent-improvements, l Y

`'Fig.-21is'a transverse sectional'view taken approximatelyo'n line 2&2l of Fig. 1,

'@Fi'g. i3 vis a longitudinal sectional view re'- semlbling/Fig. 1 'butfon a substantially enlarged soa e,

tallic ring which serves the dual purpose of getter mount and electrostatic lensy Fig. 6 is a perspective View of the dual purpose ring featured in Fig. 5, and

Fig. '7 is a schematic View illustrating diagrammatically the various elements with which the present improvement concerns itself as well as a representative arrangement of control potentials respecting the anode and lens systems of a tube.

In the accompanying drawings, the reference numeral II designates generally an outer glass envelope which encloses the chamber in which are contained the various functioning elements of a picture tube. In the neck portion I2 of this envelope there is contained a preformed sub-assembly of apparatus generally referred to as the gun.

This sub-assembly consists of a cathode emitter I3, Fig. '7, heated by an incandescent heater I4 and contained in an apertured control grid I5. By regulating the negative bias which is induced on grid I5 there is controlled the emission intensity of the beam I6 which emerges from the grid aperture and thereby is determined the fluctuating light and dark characteristics of the scanning beam.

The electrons which emanate from the cathode are as usual negative and hence become accelerated through the positive influence of a succession of anodes indicated I'I, I8 and I9, the latter constituted predominantly of an inner surface coating of the tube envelope of carbonaceous electrically conductive material, commercially identified as Aquedag.

As the beam traverses the biased slash 2|, which intervenes between the primary anode I7 and the intermediate anode I8, it undergoes the so-called ion trap phenomenon as a result of which it is iirst deflected to one side by the unl evenness of the metallic distribution and is then realigned by the magnetic coil 22. Emerging from the intermediate anode I8, it is subjected to the action of `a pair of anodic lens ringsA 23 and 24, usually but not necessarily of identical potential.

As shown in Fig. 3, the discs which constitute lens rings 23 and 24 in a uni-potential lens system are held apart by peripheral spacers 25 to which they are spot welded and for convenience in centering and assembling theseI discs are apertured `as at 26 for receiving the innermost legs 21, see Fig. 3, of a series of equally spaced radial tension elements 28, which also constitute contacts communicating with the Aquedag in the neck of the tube.

The base end of the neck portion I2 is cemented within a plug base 29 which is provided with a locating core 3I and a series of terminal prods 32. Each one of the prods 32 is in electrical communication through a lead wire with a predetermined one of the gun assembly elements and by tting into a socket in which are provided contacting tubes that have wiping en gagement with the prods 32 the properelectrical potentials are communicated from the main circuit to the various elements of the tube.

The Aquedag coating is usually in electrical communication with its potential through a surface penetrating connection 33, Fig. 7, and by extending into the neck of the tube to a position 34 well below the resilient hairpin elements 28 this same potential prevails throughout the intermediate :anode elements :of the gun assembly.

In accordance with the usual practice, the

control grid is supported on a plurality of metallic posts which are bedded in the glass that forms the base end of the neck. The spacing between the grid, nrst anode, and intermediate anode is maintained stable by having a plurality of radially jutting anchor pins 36, Fig. 3, whose flattened ends are imbedded within a series of longitudinal glass support posts 31.

The dual purpose lens ring 4I which constitutes an essential feature of the present invention is an annular ring of sheet metal preferably having a diameter significantly larger than the apertures of the lens rings 23 and 24 and preformed by stamping with a plurality of shallow depressions as at 42, Fig. 3. Into each of these depressions is secured a getter pellet 43 which may be composed of any suitable oxidizing conipound customarily utilized for this purpose. The lens ring 4I is disposed substantially intermediate the lens rings 23 and 24 and is supported on mount posts, two of which 44 are shown to be of Short length, having their laterally extending ends imbedded in the glass mount posts 45, while the third 4G is of considerably greater length. communicating with one of the terminal prods 32 through which its electrical potential is supplied.

In operation the lens ring 4I, being made of thin sheet stock, serves primarily as an instantly responsive inductive element for ring its contained getter pellets during the manufacture and assembling of the tube when a high frequency induction coil is placed around the neck I2 of the tube, causing the temperature of the ring 4I to be raised to the level required for firing the getters.

During the utilization of the ring in television operation it has been found to exert a convergence eiect upon the beam I6 as it emerges from the central aperture of lens ring 23. A relatively low potential charge impressed upon ring 4I has been found toZ be adequate to produce a desired convergence so that the beam on reaching the screen 5I achieves an ideal point concentration. When the scanning coils 52 and 53 which are impressed with the synchronized sweep circuit currents cause the beam to describe the line for line picture surface area, the converged .beam satisfactorily maintains its physical dimensions and its concentration intensity through-out its full eld of displacement.

While the present invention has been explained and described with reference to a particular embodiment of structure, it Wil be understood nevertheless that it is susceptible to various modifications and variations. Accordingly, it is not intended that this invention be limited in scope by the particular features illustrated in the accompanying drawings, nor by the language employed in the foregoing detailed description, except as indicated in the hereunto appended claims.

The invention claimed is:

1. In a television picture tube apparatus, a dual purpose element comprising in combination with a gun assembly structure having at its forward end a pair of electrostatic lens discs and an annular'lens ring formed of thin metal peripherally studded with getter pellets, a support rod for said lens ring communicating with an external source of electric potential, and additional support means for stabilizing said ring in predetermined spacing from and in concentricity with an endmost one of said lens discs.

2. In a television picture tube apparatus, a

ray-emitting gun assembly comprising, a cathode, a control grid for regulating the intensity of emission from said cathode, a primary anode in axial'alignment with said control grid, an intermediate anode spaced from said primary anode, an endmost electrostatic lens disc terminating said intermediate anode, and a dual purpose lens ring spaced from said lens disc and having a plurality of peripheral depressions for containing getter deposits -to be fired during the manufacturing completion of said tube.

3. In a television picture tube apparatus the combination of a cathode ray tube gun assembly having atits forward end a high potential lens disc, a lens cylinder cooperating with said disc peripherally studded with getter pellets, a support rod for said cylinder constituting an electrical connection therefor, and additional support means for stabilizing said cylinder in predetermined spacing from and concentricity with said lens disc.

4. In Va television picture tube apparatus, a cathode ray gun assembly comprising a cathode, a control grid for regulating the intensity of emission from said cathode, a primary anode cylindex' in axial alignment with said control grid,

'fired during the manufacturing completion of said tube.

5. In a television picture tube, a gun assembly including in combination with a cathode, a grid, and a cylindrical anode terminated by a high potential lens disc, a low voltage lens cylinder spaced from said disc to induce a divergent effect upon the scanning beam emanating from said cathode and mounting a plurality of getter pellets on its periphery whereby to be simultaneously fired when said cylinder is inductively heated following the sealing of said tube.

ANACLETO D. GIACCHETTI.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,873,683 Von Wedel Aug. 23, 1932 2,242,100 Atlee 'May 13, 1941 2,341,941 Mouromtseff et al. Feb. 15, 1944 

